The invention relates to a clamping device of a workpiece on a tool, of the type comprising a flange actuated by a cylinder, which retracts and which moves linearly in the clamping phase.
Such a clamping device is known from document FR 2 863 190, a patent application filed by the present inventor. This device comprises a body comprising a lower part of cylindrical form and an upper part in the form of a clevis. A flange is mounted mobile between the two wings of the clevis and is actuated by the rod of a cylinder housed in the lower part. The flange moves between a gripping position and a release position. Movement from the gripping position to the release position comprises a first translation phase parallel to the axis of the cylinder followed by a rotation phase to give access to the tool to remove the workpiece and place another. Movement from the release position to the gripping position follows the same trajectory, in the reverse direction of the preceding.
In the positions of the translation phase, the flange is guided by support elements made by heels of the flange and support surfaces of the wings of the clevis. It is also guided by a pivot at the end of the rod. The geometry of the triangle formed by the axis of the pivot, the support elements and the point of contact of the flange on the workpiece determines amplification of forces applied to the workpiece and which are transmitted in the form of torque between the pivot and the support elements.
Such a device is entirely satisfactory, in particular in terms of quick actuation and compactness, when the support point on the workpiece can be near the device. However, in some configurations, it is preferable, or even indispensable, for this support point to be away from the clamping device due to the stresses of the geometry of the workpiece. This is possible by elongation of the flange, but such elongation increases stresses on the pivot and the support elements or limits the clamping force if said stresses cannot increase. Also, this elongation leads to larger bulk in the release position. In fact, the flange has pivoted by around a quarter turn towards upwards and its length is added to that of the body in the direction of the cylinder.
A possible solution for increasing admissible forces is to move the support elements away from the position of the pivot in the gripping position. This in turn increases the length of the body and the height of the flange, which increases the bulk of the device both in gripping position and in release position. This solution therefore is not optimal due to this excessive bulk.